Ventricular Tachycardia

Definition

Ventricular Tachycardia (VT) is a broad complex tachycardia originating in the ventricles.

There are several different varieties of VT — the most being Monomorphic VT.

Monomorphic ventricular tachycardia

Clinical Significance

Ventricular tachycardia may impair cardiac output with consequent hypotension, collapse, and acute cardiac failure. This is due to extreme heart rates and lack of coordinated atrial contraction (loss of “atrial kick”).

The presence of pre-existing poor ventricular function is strongly associated with cardiovascular compromise.

Decreased cardiac output may result in decreased myocardial perfusion with degeneration to VF.

Prompt recognition and initiation of treatment (e.g. electrical cardioversion) is required in all cases of VT.

Although there is a broad complex tachycardia (HR > 100, QRS > 120), the appearance in V1 is more suggestive of SVT with aberrancy, given that the the complexes are not that broad (< 160 ms) and the right rabbit ear is taller than the left.

However, on closer inspection there are signs of AV dissociation, with superimposed P waves visible in V1.

Also, the presence of a northwest axis and an rS complex in V6 (tiny R wave, deep S wave) indicate that this is VT.

AV dissociation: superimposed P waves at a different rate to the QRS complexes

Differential Diagnosis of Wide-Complex Tachycardia

Several arrhythmias can present as a wide-complex tachycardia (QRS > 120 ms) including:

Ventricular Tachycardia

SVT with aberrant conduction due to bundle branch block

SVT with aberrant conduction due to the Wolff-Parkinson-White syndrome

Clinical Features Suggestive of VT

Age > 35 (positive predictive value of 85%)

Structural heart disease

Ischaemic heart disease

Previous MI

Congestive heart failure

Cardiomyopathy

Family history of sudden cardiac death (suggesting conditions such as HOCM, congenital long QT syndrome, Brugada syndrome or arrhythmogenic right ventricular dysplasia that are associated with episodes of VT)

Diagnostic Algorithms

A number of diagnostic algorithms exist to help aid in the diagnosis of VT.

No algorithm is 100% accurate in predicating VT

Algorithms can be complex and require specific and unfamiliar measurements to be calculated

Flow charts for the four commonly used algorithms (ACC, Brugada, Ultra-simple Brugada, Vereckei ) can be found here.

About Edward Burns

Ed Burns is an Emergency Physician working in Prehospital & Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education. Ed is the force behind the LITFL ECG library | + Edward Burns | @edjamesburns